When I bought the jeep I was aware of a problem but i have yet to be able to figure out whats wrong. When I let off the gas pedal while driving I hear a clunk about 70% of the time and very rarely it when shifting into reverse it makes a grinding noise(a prety loud one at that. The rear axle is newer. Ujoints? transfercase? Please help

 

check your u joints in the rear shaft, then inspect the slip joint @ the transfercase, lube the splines

 

That could cause the grinding from what sounds like its coming from near the rear of the vehicle?